Note 9 - Business Segments - Reconciling Information Between Reportable Segments and Consolidated Totals (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Total consolidated revenues	$ 166,480	$ 157,185	$ 528,802	$ 526,447
Operating income	25,902	43,970	117,128	156,618
Interest income	214	255	516	861
Interest expense, net	(18,700)	(11,692)	(48,890)	(41,155)
Derivatives and foreign currency transaction gains (losses)	(383)	(1,001)	(2,511)	2,040
Income attributable to sale of tax benefits	4,066	3,506	14,983	14,019
Other non-operating income (expense), net	309	(1,592)	7,662	(1,678)
Total consolidated income before income taxes and equity in income of investees	11,408	33,446	88,888	130,705
Intersegment Eliminations [Member]
Total consolidated revenues	9,236	28,248	45,516	61,026
Consolidation, Eliminations [Member]
Total consolidated revenues	$ (9,236)	$ (28,248)	$ (45,516)	$ (61,026)